Lines Matching +full:frame +full:- +full:buffer
1 The Frame Buffer Device
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4 Maintained by Geert Uytterhoeven <geert@linux-m68k.org>
9 ---------------
11 The frame buffer device provides an abstraction for the graphics hardware. It
12 represents the frame buffer of some video hardware and allows application
13 software to access the graphics hardware through a well-defined interface, so
14 the software doesn't need to know anything about the low-level (hardware
22 --------------------------
24 From the user's point of view, the frame buffer device looks just like any
26 specifies the frame buffer number.
31 0 = /dev/fb0 First frame buffer
32 1 = /dev/fb1 Second frame buffer
34 31 = /dev/fb31 32nd frame buffer
39 /dev/fb0current -> fb0
40 /dev/fb1current -> fb1
44 The frame buffer devices are also `normal' memory devices, this means, you can
49 There also can be more than one frame buffer at a time, e.g. if you have a
50 graphics card in addition to the built-in hardware. The corresponding frame
51 buffer devices (/dev/fb0 and /dev/fb1 etc.) work independently.
53 Application software that uses the frame buffer device (e.g. the X server) will
55 an alternative frame buffer device by setting the environment variable
56 $FRAMEBUFFER to the path name of a frame buffer device, e.g. (for sh/bash
65 After this the X server will use the second frame buffer.
69 --------------------------------
71 As you already know, a frame buffer device is a memory device like /dev/mem and
74 appears in the special file is not the whole memory, but the frame buffer of
82 - You can request unchangeable information about the hardware, like name,
86 - You can request and change variable information about the hardware, like
92 - You can get and set parts of the color map. Communication is done with 16
104 etc.), because it works on the frame buffer image data directly.
106 For the future it is planned that frame buffer drivers for graphics cards and
113 3. Frame Buffer Resolution Maintenance
114 --------------------------------------
116 Frame buffer resolutions are maintained using the utility `fbset'. It can
117 change the video mode properties of a frame buffer device. Its main usage is
126 ---------------
128 The X server (XF68_FBDev) is the most notable application program for the frame
129 buffer device. Starting with XFree86 release 3.2, the X server is part of
132 - If the `Display' subsection for the `fbdev' driver in the /etc/XF86Config
144 - Therefore it's also possible to specify resolutions in the /etc/XF86Config
145 file. This allows for on-the-fly resolution switching while retaining the
146 same virtual desktop size. The frame buffer device that's used is still
149 specify the timings in a different format (but `fbset -x' may help).
156 ---------------------
169 whole screen (frame) was painted, the beam moves back to the upper left corner:
177 1/(28.37516E6 Hz) = 35.242E-9 s
181 640*35.242E-9 s = 22.555E-6 s
186 (640+272)*35.242E-9 s = 32.141E-6 s
190 1/(32.141E-6 s) = 31.113E3 Hz
195 (480+49)*32.141E-6 s = 17.002E-3 s
199 1/(17.002E-3 s) = 58.815 Hz
209 vsync) for each new frame. The position of the image on the screen is
217 +----------+---------------------------------------------+----------+-------+
221 +----------###############################################----------+-------+
228 |<-------->#<---------------+--------------------------->#<-------->|<----->|
242 +----------###############################################----------+-------+
246 +----------+---------------------------------------------+----------+-------+
250 +----------+---------------------------------------------+----------+-------+
252 The frame buffer device expects all horizontal timings in number of dotclocks
253 (in picoseconds, 1E-12 s), and vertical timings in number of scanlines.
256 6. Converting XFree86 timing values info frame buffer device timings
257 --------------------------------------------------------------------
263 The frame buffer device uses the following fields:
265 - pixclock: pixel clock in ps (pico seconds)
266 - left_margin: time from sync to picture
267 - right_margin: time from picture to sync
268 - upper_margin: time from sync to picture
269 - lower_margin: time from picture to sync
270 - hsync_len: length of horizontal sync
271 - vsync_len: length of vertical sync
280 left_margin = HFL - SH2
281 right_margin = SH1 - HR
282 hsync_len = SH2 - SH1
285 upper_margin = VFL - SV2
286 lower_margin = SV1 - VR
287 vsync_len = SV2 - SV1
294 -------------
296 For more specific information about the frame buffer device and its
297 applications, please refer to the Linux-fbdev website:
299 http://linux-fbdev.sourceforge.net/
303 - The manual pages for fbset: fbset(8), fb.modes(5)
304 - The manual pages for XFree86: XF68_FBDev(1), XF86Config(4/5)
305 - The mighty kernel sources:
313 ---------------
315 There is a frame buffer device related mailing list at kernel.org:
316 linux-fbdev@vger.kernel.org.
318 Point your web browser to http://sourceforge.net/projects/linux-fbdev/ for
323 --------------
327 ftp://ftp.uni-erlangen.de/pub/Linux/LOCAL/680x0/
333 http://www.linux-fbdev.org/
337 ----------
340 `X-framebuffer.README' by Roman Hodek and Martin Schaller. Section 6 was
343 The frame buffer device abstraction was designed by Martin Schaller.